Security camera systems often monitor areas where individuals are not normally present for substantial periods of time, such as display cases containing store merchandise during non-business hours or activities within bank vaults. Typically, such security camera systems employ video recording equipment to record images of the viewed area. Since no or little motion occurs within these viewed areas over long periods of time it is desirable to record images of the viewed area only when motion occurs. Such motion may be caused by individuals, whether lawfully or illegally, entering the viewed area.
Some prior art security cameras have employed external motion detectors, such as infra-red or microwave motion detector devices, to activate the recording equipment associated with the cameras when motion is detected in the viewed area. A drawback to such systems is there high cost and bulk. Typically, the relative large size of the camera and motion detector arrangement of the system are unsightly and difficult to hide.
A smaller prior art motion detection arrangement employs a video camera, an analog-to-digital converter, a frame buffer and a system controller to detect motion by sensing interframe differences in the video signal generated by the video camera. In this arrangement, the video signal generated by the camera is digitized by the analog-to-digital converter. The digitized signal for each video frame is temporally buffered in the frame buffer where the controller compares it with the respective next generated frame information to detect if motion has occurred between the frames. When motion is detected, the video signal is provided to a recording device. Although this arrangement eliminates the need for a separate motion detector, it is complex and costly.
Therefore, a need exists for a low cost, compact security camera system with built-in motion detection.